Compact portable electronic devices are becoming increasingly popular. Examples of compact portable electronic devices include laptop computers, tablet computing devices, cellular telephones, media players, gaming devices, handheld devices, miniature devices such as pendant and wearable devices, and other devices. It is generally desirable to reduce both internal and external interference of the components in the compact portable electronic devices. The interference can be reduced or eliminated using electromagnetic shielding. For example, some electronic devices include radio-frequency transceiver circuits that are susceptible to radio-frequency interference. Electronic devices can also include memory and other components that use clock signals during normal operation. If care is not taken, signals from one circuit can interfere with the proper operation of another circuit. For example, a clock signal or a clock signal harmonic that falls within the operating band of a radio-frequency receiver can cause undesirable interference for a radio-frequency transceiver.
To protect devices from electromagnetic interference, circuits such as radio-frequency transceivers can be enclosed within metal shielding cans, or a conductive paste can be disposed between the circuits. The metal of the shielding cans or the conductive paste can block signals and can help shield the enclosed components from electromagnetic interference. To reduce the size of compact portable electronic devices, the circuitry can be integrated into a System-in-Package. However, shielding cans and conductive paste can limit the effectiveness of the shielding and can limit the size of the device. An alternative to the metal shielding cans and conductive paste are thin-film metal layers. However, the thin-film metal layers can have limited shielding effectiveness, poor adhesion to underlying layers, can be aesthetically unappealing, and can be susceptible to environment-induced degradation or discoloration.